If nothing else I would recommend mapping the barriers. Most data consumers will treat these so as not to route through them, foot=no is a failsafe.
I’m generally in favour of leaving old trails in the database marked with disused:highway or similar: as others have said the main purpose is to discourage people from adding them back. This includes not just people using aerial imagery (or GPS/Strava traces, or out-of-date trail maps), but people intimately familiar with an area who haven’t been there for a while. It’s quite easy to decide that a familiar area is missing detail, when actually it had the detail but it has since gone and been removed from OSM.